The present invention is directed to devices and methods for concentrating fluids. More particularly, the present invention is directed to devices and methods for concentrating body fluids such as blood, with the concentration steps including both a centrifugation act and a filtration act.
Concentration and/or filtration of body fluids has long been practiced in the medical arts. Of the various body fluids which may be concentrated or filtered, blood is perhaps the most common. Blood is commonly filtered to remove impurities or waste products (kidney dialysis, for example). Blood is commonly concentrated into different components, such as white blood cells, plasma, or red blood cells, for use in a wide variety of handling options and treatment modalities. In some instances, the filtration or concentration of blood components is not critically time sensitive, but rather can be carried out over a period of hours or days. In other instances, particularly when a patient's own blood is being filtered and/or concentrated and then immediately returned to the patient's body, the filtration and/or concentration process must be completed in a more time sensitive manner, such as within a matter of minutes. The present invention is particularly appropriate for use in time sensitive situations, and to reduce the handling time as compared to the prior art.
In some applications, the filtration and/or concentration process is carried out in an ongoing, streaming process, wherein the body fluid is simultaneously removed from the patient's body and then downstream returned to the patient's body. In other applications, the filtration and/or concentration process is carried out in a batch process, wherein an amount of the body fluid is removed from the body as a unit, treated, and then returned to the patient's body as a unit. The present invention is particularly intended for batch processing.
For body fluids which can be treated in a batch process, centrifugation is a common method of concentration. For example, a batch of blood may be removed as a unit and placed into a centrifuge vessel. The centrifuge vessel is spun at high speed, subjecting the blood to a centrifugal force which can be tens or hundreds of times the force of gravity. Under this centrifugal force, the blood separates into different components based to an extent on molecular weight, such as separation of red blood cells, platelet poor plasma, and an intermediate plasma fraction known as “buffy coat”.
More recently, blood fractions separated by centrifugation have been further filtered to increase cell or component concentrations in the filtrate. U.S. Pat. Nos. 5,733,545, 6,010,627 and 6,342,157 to Hood, III show examples of this, and are incorporated by reference. Such concentrated, centrifuged body fluids have been shown to be useful in various treatment modalities, such as applying the concentrated blood component directed to an orthopedic wound site. However, the methods and devices taught in these Hood, III patents have shortcomings which have prevented widespread acceptance and use in an operating environment.